Should Speaker Manufactures provide a Frequency Response Graph?

 I agree with erik_squires.  A frequency response chart made in an anechoic room has little to do with how that speaker will sound in your room with your amplifier.  Besides, the impedance of the speaker is changing with frequency which will affect how your amplifier/speaker cables sound coupled to those speakers.

Back in the early 1990's I built my first dedicated listening room and I added sound dampening to make my room have a flat frequency response.  The room was very close to anechoic.  The music sounded dead and lifeless.  I had to remove much of the dampening material.  

That's my point, I guess.  If you want flat frequency response then you will need a hemianechoic room like the room where they test speakers.  It will not sound so good.  Think about live music.  No band ever plays in an anechoic room.  Life is messy and so is music.

“It merely requires an understanding of how the measurements correlate to perceived should quality“

Good luck with that.  A panel of listeners will rarely, if ever unanimously agree on the sound quality of a speaker or system.  On top of that, any speaker will sound different based on the room, the setup, the amps, the cables, the source, condition of the power coming into the system, etc.

“…take any two tweeters and provide a CSD/waterfall graph for each.  Based on the graphs, I could tell you with certainty…“. No, not with certainty.  You might guess right some of the time.

“… a speaker with a wider horizontal dispersion over a large bandwidth will produce a bigger soundstage than one with a narrower dispersion over the same bandwidth.“. Not really.  Careful, you are using lots of fancy terms here without context.

Have you actually designed and built a speaker?

We in this hobby are Audio Application Sound Specialists, or AASS‘s for short.  We do not design speakers, amps, DACs, cables or turntables.  We design audio systems.  Therefore, what matters most to us are the basic interface specifications of each component.  For example, for a given speaker we need power handling range, frequency response range, efficiency, impedance curve, ported/unported, size, and weight.  And finally the looks for those who don’t listen in the dark.  For more advanced work the Q factor might be beneficial to know.  Nothing in the design/development specs is going to give us much of a clue as to how the speaker sounds or images in our room along with our ancillary equipment and cables.  The speaker designer and builder is doing his best to make a product that looks pleasing, plays well with various amps and is reliable all while meeting a price point.  I have been known to blow a tweeter or two in my day.